Color erasing apparatus, color erasing system and color erasing control method

ABSTRACT

In accordance with one embodiment, a color erasing apparatus comprises a conveyance path, a color erasing section and a control section. The conveyance path conveys a sheet. The color erasing section erases the color of an image formed with color erasable recording agent serving as recording agent containing coloring agent the color of which can be erased by heating. The control section carries out a control, in a case where the image formed on the sheet is not an image formed with the color erasable recording agent, so that the sheet is not subjected to a color erasing processing by the color erasing section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 15/002,585filed on Jan. 21, 2016, which is a Continuation of application Ser. No.14/287,939 filed on May 27, 2014, the entire contents of both of whichare incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a color erasingapparatus, color erasing system and a color erasing control method.

BACKGROUND

In recent years, in an image forming apparatus such as a MFP (MultiFunction Peripheral), an image is formed on a sheet-like medium(hereinafter referred to as “sheet”) such as paper with recording agent(hereinafter referred to as “color erasable recording agent”) containingerasable coloring agent. The color of the color erasable recording agentcan be erased when heated to a high temperature.

A heat roller, in which a roll type heat source is arranged, and a pressroller are arranged opposite to each other in the color erasingapparatus. The color erasing apparatus heats paper with the heat rollerand the press roller to erase the color of the image formed on thepaper.

However, if a sheet on which an image is formed with recording agent(for example, normal toner) different from the color erasable recordingagent is conveyed to the heat roller (heat source) of the color erasingapparatus, offset may occur on the heat roller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an example of theconstitution of a color erasing apparatus 1 according to one embodiment;

FIG. 2 is a block diagram illustrating an example of the constitution ofthe functions of the color erasing apparatus 1 according to theembodiment;

FIG. 3 is a diagram illustrating a specific example of a sheet on whichan image is formed with color erasable recording agent;

FIG. 4 is a diagram illustrating a specific example of a sheet on whichan image is formed with color erasable recording agent;

FIG. 5 is a diagram illustrating a specific example of a sheet on whichan image is formed with color erasable recording agent;

FIG. 6 is a diagram illustrating a specific example of a colordifference table used when an image processing section 66 detects agiven image 74;

FIG. 7 is a flowchart illustrating a first specific example of theoperations carried out by the color erasing apparatus 1;

FIG. 8 is a flowchart illustrating a second specific example of theoperations carried out by the color erasing apparatus 1;

FIG. 9 is an external view illustrating an example of the constitutionof an image forming apparatus 100; and

FIG. 10 is a block diagram illustrating an example of the functionalconstitution of the image forming apparatus 100.

DETAILED DESCRIPTION

In accordance with one embodiment, a color erasing apparatus comprises aconveyance path, a color erasing section and a control section. Theconveyance path conveys a sheet. The color erasing section erases thecolor of an image formed with color erasable recording agent serving asrecording agent containing coloring agent the color of which can beerased by heating. The control section carries out a control, in a casewhere the image formed on the sheet is not an image formed with thecolor erasable recording agent, so that the sheet is not subjected to acolor erasing processing by the color erasing section.

The color erasing apparatus according to embodiment is described belowwith reference to the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating an example of theconstitution of the color erasing apparatus 1 according to theembodiment.

The color erasing apparatus 1 erases the color of the image formed on asheet with color erasable recording agent (for example, color erasabletoner, color erasable ink, color erasable ink ribbon and the like). Inthe present embodiment, toner is used as the color erasable recordingagent. Paper, film and the like may be listed as one example of thesheet. The “color-erasing” mentioned herein refers to changing the colorof the image formed with the color erasable recording agent to reducethe visibility of the image. The color-erased sheet can be reused. Forexample, the color-erased sheet can be reused as a sheet to be formedwith an image by the image forming apparatus.

The color erasing apparatus 1 comprises a control panel 10, a paper feedsection 20, a reading section 30, a color erasing section 40, a paperdischarge section 50 and a control section 60. The color erasingapparatus 1 conveys the sheet loaded in the paper feed section 20 to thecolor erasing section 40. The color erasing apparatus 1 erases the colorof the image on the sheet conveyed to the color erasing section 40.Then, the color erasing apparatus 1 discharges the color-erased sheet tothe paper discharge section 50.

The color erasing apparatus 1 is provided with conveyance paths RT1˜RT6.The conveyance paths RT1˜RT6 convey the paper in the color erasingapparatus 1. A plurality of motors M, a plurality of conveyance rollersR, a plurality of platen rollers PR and a plurality of sensors S arearranged on the conveyance paths RT1˜RT6.

The motor M drives the conveyance roller R. The driven conveyance rollerR conveys the sheet. The platen roller PR is arranged opposite to theconveyance roller R to press the sheet so that the sheet is properlyconveyed. The sheet is conveyed along the conveyance paths RT1˜RT6 bythe conveyance roller R and the platen roller PR.

The sensor S detects the existence of the sheet. The position of thesheet in the color erasing apparatus 1 is detected by the sensor S.

The control panel 10 functions as a user interface. The control panel 10is provided with an operation section and a display section. Theoperation section of the control panel 10 receives an operationinstruction of the color erasing apparatus 1 based on the operationcarried out by an operator. The display section of the control panel 10displays information to the operator.

The paper feed section 20 is provided with a paper feed tray 21, a paperfeed roller 22 and a sensor S.

The paper feed tray 21 is a table for loading the sheet to be subjectedto color erasing processing. The sheet to be subjected to color erasingprocessing is a sheet on which an image is formed with color erasablerecording agent. The paper feed roller 22 feeds the sheets, one by one,loaded on the paper feed tray 21 to the conveyance path RT1.

The reading section 30 detects the state of the sheet conveyed by theconveyance path RT2. A specific example of the reading section 30 isdescribed below. The reading section 30 comprises a line scanner 31, aline scanner 32 and platen rollers. The reading section 30 captures theimage formed on the front side of the sheet and the image formed on theback side of the sheet.

The color erasing section 40 executes a processing (hereinafter referredto as “color erasing processing”) of erasing the color of image on thesheet conveyed on the conveyance path RT3. A specific example of thecolor erasing section 40 is described below. The color erasing section40 is provided with a thermal head 41 and a platen roller. The thermalhead 41 of the color erasing section 40 has a plurality of heatgenerating elements. The color erasing section 40 erases the color ofthe image formed on the front side of the sheet and the image formed onthe back side of the sheet based on the heat generated by the heatgenerating elements. In addition, the color-erased image is an imageformed with the color erasable recording agent.

The paper discharge section 50 discharges the sheet conveyed on theconveyance path RT4 through the conveyance path RT5 or the conveyancepath RT6. The paper discharge section 50 includes a reuse tray 51 and areject tray 52. The reuse tray 51 stores the sheet discharged throughthe conveyance path RT5. The reject tray 52 stores the sheet dischargedthrough the conveyance path RT6.

The reuse tray 51 is a stocker for storing a reusable sheet. The rejecttray 52 is a stocker for storing a not-reusable sheet.

One end of the conveyance path RT1 is connected with the paper feed tray21. The other end of the conveyance path RT1 is connected with theconveyance path RT2. The conveyance path RT1 guides the sheet fed by thepaper feed section 20 to the conveyance path RT2.

One end of the conveyance path RT2 is connected with the conveyance pathRT1. The other end of the conveyance path RT2 is connected with a branchpoint of the conveyance path RT3 and the conveyance path RT4. Thereading section 30 is arranged in the middle of the conveyance path RT2.The conveyance path RT2 feeds the sheet passing the conveyance path RT1to the reading section 30. The conveyance path RT2 guides the sheetpassing through the reading section 30 to the conveyance path RT3 or theconveyance path RT4. In the following description, the conveyance pathRT2 is referred to as a first conveyance path as needed.

Agate GT1 is arranged at the branch point of the conveyance path RT3 andthe conveyance path RT4. The gate GT1 switches the conveyance path ofthe sheet conveyed by the conveyance path RT2 to either of theconveyance path RT3 and the conveyance path RT4. In a case of carryingout color erasing processing on the sheet conveyed on the conveyancepath RT2, the gate GT1 guides the sheet to the conveyance path RT3 basedon the control of the control section 60. In a case of discharging thesheet conveyed on the conveyance path RT2, the gate GT1 guides the sheetto the conveyance path RT4 based on the control of the control section60.

One end of the conveyance path RT3 is connected with the conveyance pathRT2 through the gate GT1. The other end of the conveyance path RT3 isconnected with the conveyance path RT2. The color erasing section 40 isarranged in the middle of the conveyance path RT3. The conveyance pathRT3 feeds the sheet passing the conveyance path RT2 to the color erasingsection 40. The conveyance path RT3 guides the sheet passing through thecolor erasing section 40 to the conveyance path RT2. In the followingdescription, the conveyance path RT3 is referred to as a secondconveyance path as needed.

One end of the conveyance path RT4 is connected with the conveyance pathRT2 through the gate GT1. The other end of the conveyance path RT4 isconnected with the branch point of the conveyance path RT5 and theconveyance path RT6. The conveyance path RT4 guides the sheet passingthe conveyance path RT2 to the conveyance path RT5 or the conveyancepath RT6.

Agate GT2 is arranged at the branch point of the conveyance path RT5 andthe conveyance path RT6. The gate GT2 switches the conveyance path ofthe sheet conveyed by the conveyance path RT4 to either of theconveyance path RT5 and the conveyance path RT6. If the sheet conveyedon the conveyance path RT4 is a reusable sheet, the gate GT2 guides thesheet to the conveyance path RT5 based on the control of the controlsection 60. If the sheet conveyed on the conveyance path RT4 is anot-reusable sheet, the gate GT2 guides the sheet to the conveyance pathRT6 based on the control of the control section 60.

One end of the conveyance path RT5 is connected with the conveyance pathRT4 through the gate GT2. The other end of the conveyance path RT5 isconnected with the reuse tray 51. The conveyance path RT5 guides thesheet passing the conveyance path RT4 to the reuse tray 51.

One end of the conveyance path RT6 is connected with the conveyance pathRT4 through the gate GT2. The other end of the conveyance path RT6 isconnected with the reject tray 52. The conveyance path RT6 guides thesheet passing the conveyance path RT4 to the reject tray 52.

FIG. 2 is a block diagram illustrating an example of the functionalconstitution of color erasing apparatus 1 according to the embodiment.

The control section 60 comprises a main CPU (Central Processing Unit)61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, aconveyance control section 64, a scanner control section 65, an imageprocessing section 66, an image RAM 67 and a thermal head controlsection 68. The control section 60 controls the control panel 10, theplurality of sensors S, the plurality of motors M, the plurality ofgates (GT1 and GT2), the reading section 30 and the color erasingsection 40.

The main CPU 61 uniformly controls the color erasing apparatus 1. Themain CPU 61 executes programs to execute various processing. The mainCPU 61 acquires an instruction input by the operator from the controlpanel 10. The main CPU 61 executes control processing based on theacquired operation instruction. The main CPU 61 displays a processingresult and the information relating to the next operation on the controlpanel 10.

The ROM 62, which is a non-volatile memory, stores the program forexecuting the control processing, the control data and the like.

The RAM 63, which is a volatile memory, functions as a working memoryand a buffer memory. The RAM 63 temporarily stores the data used in theprocessing carried out by the control section 60.

The conveyance control section 64 controls the conveyance of the sheetin the color erasing apparatus 1. A specific example of the processingcarried out by the conveyance control section 64 is described below. Theconveyance control section 64 detects the position of the sheet in thecolor erasing apparatus 1 based on the output of the plurality ofsensors S. The conveyance control section 64 outputs the detectionresult indicating the position of the sheet to the main CPU 61.

The conveyance control section 64 controls the driving of the pluralityof motors M and the gates (GT1 and GT2) in response to the instructionof the main CPU 61. For example, the conveyance control section 64drives the motor M to rotate the paper feed roller 22 in response to astart instruction of the color erasing processing received from the mainCPU 61. The sheet loaded on the paper feed tray 21 is fed through therotation of the paper feed roller 22.

The conveyance control section 64 may control the driving of a pluralityof motors M based on the detection result indicating the position of thesheet. For example, the conveyance control section 64 drives the motorsM to rotate a plurality of conveyance rollers R in response to theposition of the sheet. The sheet is conveyed on the conveyance paththrough the rotation of the conveyance roller R.

The scanner control section 65 controls the line scanner 31 and the linescanner 32 in response to the instruction received from the main CPU 61if the sheet is conveyed to the reading section 30. For example, thescanner control section 65 operates the line scanner 31 and the linescanner 32 to acquire the image data representing the image on thesheet. For example, the image data of the front side of the sheet isacquired through the operation of the line scanner 31, and the imagedata of the back side of the sheet is acquired through the operation ofthe line scanner 32. The scanner control section 65 outputs the acquiredimage data to the image processing section 66.

The image processing section 66 acquires the image data output by thescanner control section 65 and stores the acquired image data in theimage RAM 67. The image processing section 66 reads the image data fromthe image RAM 67. The image processing section 66 generates pattern datawhich will be used in the image color-erasing processing of the colorerasing section 40 based on the read image data of the front side andthe image data of the back side. The image processing section 66 storesthe generated pattern data in the image RAM 67.

The pattern data is used when the thermal head 41 is driven. The patterndata contains, for example, color erasing data for controlling the heatgeneration for each of the plurality of heat generating elements of thethermal head 41. The color erasing data is the information indicatingwhether or not there is an image formed at the position. For example,the color erasing data indicates whether or not there is image data tobe subjected to color erasing processing for each unit block arranged onthe sheet.

The image processing section 66 reads the pattern data from the imageRAM 67 based on the instruction of the main CPU 61. The image processingsection 66 outputs the read pattern data to the thermal head controlsection 68.

The image processing section 66 determines whether the image is formedwith the color erasable recording agent or the color inerasablerecording agent based on the image data. The image processing section 66outputs the determination result to the main CPU 61. For example, in acase in which a given image determined in advance exists in a given area(hereinafter referred to as “detection target area”) determined inadvance, the image processing section 66 determines that the image isformed with the color erasable recording agent. In this case, the mainCPU 61 determines to execute the color erasing processing. On the otherhand, in a case in which the given image determined in advance does notexist in the detection target area, the image processing section 66determines that the image is not formed with the color erasablerecording agent. In this case, the main CPU 61 determines not to executethe color erasing processing.

The image RAM 67 is a storage section for storing the image data and thepattern data processed by the image processing section 66.

The thermal head control section 68 controls the thermal head 41 of thecolor erasing section 40 based on the pattern data. The thermal headcontrol section 68 detects that the sheet is conveyed to the colorerasing section 40 according to the output of the sensor S. The thermalhead control section 68 drives the thermal head 41 in response to theinstruction received from the main CPU 61. In a case of driving thethermal head 41 to carry out color erasing processing, the thermal headcontrol section 68 controls the heat generation of the plurality of heatgenerating elements based on the pattern data. The color erasablerecording agent is heated by the heat generating elements and the colorof the image at the heated position is erased.

FIG. 3 is a diagram illustrating a specific example of a sheet on whichan image is formed with the color erasable recording agent. An imageforming area 72 located inside the sheet 71 represents a range in whichan image relating to actual data is formed by an image forming apparatusfor forming an image on a sheet with color erasable recording agent. Theimage forming apparatus forms an image relating to actual data in theimage forming area 72. In addition, the image forming apparatus is alsocapable of forming an image outside the image forming area 72. Thus, animage relating to a header and a footer may be formed outside the imageforming area 72.

The given image 74 determined in advance exists in a detection targetarea 73 of the sheet the image on which is erased by the color erasingapparatus 1. In FIG. 3, the detection target area 73 is arranged as anarea on the sheet 71 but outside the image forming area 72.

FIG. 4 is a diagram illustrating a specific example of a sheet on whichan image is formed with the color erasable recording agent. In FIG. 4,the detection target areas 73 are arranged at the front and the rear endin the conveyance direction of the sheet in the color erasing apparatus1. The given image 74 is formed in the detection target area 73. In FIG.4, one detection target area 73 is defined as an area surrounded by aside (hereinafter referred to as “front end side”) located at the frontend in the conveyance direction of the sheet, a side which is positionedat a distance of a1 away from the front end side and is parallel to thefront end side, a right side and a left side in the conveyance directionof the sheet. In FIG. 4, another detection target area 73 is defined asan area surrounded by a side (hereinafter referred to as “rear endside”) located at the rear end in the conveyance direction of the sheet,a side which is positioned at a distance of a1 away from the rear endside and is parallel to the rear end side, a right side and a left sidein the conveyance direction of the sheet.

FIG. 5 is a diagram illustrating a specific example of a sheet on whichan image is formed with the color erasable recording agent. In FIG. 5,the detection target areas 73 are defined in a more restrictive manner.In FIG. 5, one detection target area 73 is defined as an area surroundedby the front end side, a side which is positioned at a distance of a1away from the front end side and is parallel to the front end side, aside which is positioned at a distance of a2 away from the left side inthe conveyance direction of the sheet and is parallel to the left side,and a side which is positioned at a distance of (a2+a3) away from theleft side in the conveyance direction of the sheet and is parallel tothe left side. In FIG. 5, another detection target area 73 is defined asan area surrounded by the rear end side, a side which is positioned at adistance of a1 away from the rear end side and is parallel to the rearend side, a side which is positioned at a distance of a2 away from theright side in the conveyance direction of the sheet and is parallel tothe right side, and a side which is positioned at a distance of (a2+a3)away from the right side in the conveyance direction of the sheet and isparallel to the right side.

FIG. 6 is a diagram illustrating a specific example of a colordifference table used when the image processing section 66 detects thegiven image 74. The image processing section 66 detects the given image74 in a case where the color difference between the color of the sheetand the color of the given image 74 is greater than a threshold value.The color difference table displays the preset threshold value of thecolor difference for each color of the sheet.

For example, the color difference table includes a plurality of records91. The record 91 includes the values of the color of a sheet and thethreshold value. The value of the color of a sheet represents the colorof the part on the sheet where no image is formed. The threshold valuerepresents the threshold value of the color difference when the imageformed on the sheet having a color of the sheet of the same record 91 isrecognized as an image. For example, in a case where the colordifference between the color of a certain area on a white sheet and thecolor of the sheet is greater than t1, the image processing section 66determines the area as a part where an image exists. For example, in acase where the color difference between the color of a certain area on awhite sheet and the color of the sheet is less than t1, the imageprocessing section 66 determines the area as a part where the color isthe color of the sheet.

FIG. 7 is a flowchart illustrating a first specific example of theoperations carried out by the color erasing apparatus 1. First, thepaper feed section 20 feeds a sheet (ACT 101). Next, the conveyance pathRT1 conveys the sheet. Then, the first conveyance path (conveyance pathRT2) conveys the sheet conveyed by the conveyance path RT1 to thereading section 30 (ACT 102). The reading section 30 reads the images onthe front side and the back side of the conveyed sheet to acquire imagedata (ACT 103).

The image processing section 66 determines whether or not the image isformed with color erasable recording agent based on the acquired imagedata (ACT 104). If the image is not formed with color erasable recordingagent (NO in ACT 104), the main CPU 61 determines not to carry out colorerasing processing. In response to the determination, the main CPU 61discharges the sheet passing through the reading section 30 to thereject tray (ACT 105). Specifically, the main CPU 61 carries out thefollowing operations.

The main CPU 61 controls the gate GT1 so that the sheet passing throughthe reading section 30 is conveyed to the conveyance path RT4. The gateGT1 guides the sheet conveyed on the conveyance path RT2 to theconveyance path RT4 in response to the control of the main CPU 61. Thenthe main CPU 61 controls the gate GT2 so that the sheet passing theconveyance path RT4 is conveyed to the conveyance path RT6. The gate GT2guides the sheet conveyed on the conveyance path RT4 to the conveyancepath RT6 in response to the control of the main CPU 61. The sheetconveyed on the conveyance path RT6 is discharged to the reject tray 52.

In the operation in ACT 104, if the image is formed with color erasablerecording agent (YES in ACT 104), the main CPU 61 determines to carryout color erasing processing. In response to the determination, the mainCPU 61 conveys the sheet passing through the reading section 30 to thesecond conveyance path (conveyance path RT3) (ACT 106). Specifically,the main CPU 61 carries out the following operations.

The main CPU 61 controls the gate GT1 so that the sheet passing throughthe reading section 30 is conveyed to the conveyance path RT3. The gateGT1 guides the sheet conveyed on the conveyance path RT2 to theconveyance path RT3 in response to the control of the main CPU 61.

Next, the second conveyance path (conveyance path RT3) conveys the sheetconveyed by the first conveyance path (conveyance path RT2) to the colorerasing section 40. The color erasing section 40 erases the color of theimage on the conveyed sheet (ACT 107). The second conveyance path(conveyance path RT3) guides the sheet passing through the color erasingsection 40 to the first conveyance path (conveyance path RT2). The firstconveyance path (conveyance path RT2) conveys the sheet conveyed by thesecond conveyance path (conveyance path RT3) to the reading section 30(ACT 108). The reading section 30 reads the images on the front side andthe back side of the conveyed sheet to acquire image data (ACT 109).

The main CPU 61 determines whether or not the conveyed sheet is reusablebased on the acquired image data (ACT 110). For example, the main CPU 61calculates the percentage of the area, of which the color differencewith the color of the sheet is greater than a first given value, in thearea of the sheet. If the calculated percentage is less than a secondgiven value, the main CPU 61 determines that the sheet is reusable. Onthe other hand, if the calculated percentage is greater than the secondgiven value, the main CPU 61 determines that the sheet is not reusable.

If the sheet is determined to be not reusable (NO in ACT 110), the mainCPU 61 discharges the sheet passing through the reading section 30 tothe reject tray (ACT 105).

If the sheet is determined to reusable (YES in ACT 110), the main CPU 61discharges the sheet passing through the reading section 30 to the reusetray (ACT 111). Specifically, the main CPU 61 carries out the followingoperations.

The main CPU 61 controls the gate GT1 so that the sheet passing throughthe reading section 30 is conveyed to the conveyance path RT4. The gateGT1 guides the sheet conveyed on the conveyance path RT2 to theconveyance path RT4 in response to the control of the main CPU 61. Thenthe main CPU 61 controls the gate GT2 so that the sheet passing theconveyance path RT4 is conveyed to the conveyance path RT5. The gate GT2guides the sheet conveyed on the conveyance path RT4 to the conveyancepath RT5 in response to the control of the main CPU 61. The sheetconveyed on the conveyance path RT5 is discharged to the reuse tray 51.

FIG. 8 is a flowchart illustrating a second specific example of theoperations carried out by the color erasing apparatus 1. Compared withthe flow of the processing in the first specific example, the flow ofthe processing in the second specific example is different in theprocessing (ACT 201 and ACT 202) in a case where the image is not formedwith color erasable recording agent, and the rest of the processing isthe same as that in the first specific example. Therefore, only thepoint different from the first specific example is described.

In a case where the image on the sheet is not an image formed with colorerasable recording agent (NO in ACT 104), the main CPU 61 determines notto carry out color erasing processing. In response to the determination,the main CPU 61 conveys the sheet on the second conveyance path(conveyance path RT3) in a mode different from the color-erasing mode.

There is a plurality of embodiments for the conveyance in the modedifferent from the color-erasing mode. A first embodiment and a secondembodiment are described below.

A First Embodiment

The main CPU 61 controls the gate GT1 so that the sheet passing throughthe reading sect ion 30 is conveyed to the second conveyance path(conveyance path RT3). The gate GT1 guides the sheet conveyed on theconveyance path RT2 to the second conveyance path (conveyance path RT3)in response to the control of the main CPU 61. Then, the secondconveyance path (conveyance path RT3) conveys the sheet conveyed by thefirst conveyance path (conveyance path RT2) to the color erasing section40.

The main CPU 61 instructs the thermal head control section 68 to carryout a control so that the temperature of the thermal head 41 is lowerthan the fixing temperature of the color inerasable recording agent. Thethermal head control section 68 controls to lower the temperature of thethermal head 41 in response to the instruction of the main CPU 61. Inthis case, the offset due to the recording agent which forms an image onthe conveyed sheet is not caused.

Then, the second conveyance path (conveyance path RT3) guides the sheetpassing through the color erasing section 40 to the first conveyancepath (conveyance path RT2). The first conveyance path (conveyance pathRT2) conveys the sheet conveyed by the second conveyance path(conveyance path RT3) to the reading section 30 (ACT 202). The readingsection 30 reads the images on the front side and the back side of theconveyed sheet to acquire image data (ACT 109). The following processingis the same as that in the first specific example.

A Second Embodiment

The main CPU 61 controls the gate GT1 so that the sheet passing throughthe reading sect ion 30 is conveyed to the second conveyance path(conveyance path RT3). The gate GT1 guides the sheet conveyed on theconveyance path RT2 to the second conveyance path (conveyance path RT3)in response to the control of the main CPU 61. Then, the secondconveyance path (conveyance path RT3) conveys the sheet conveyed by thefirst conveyance path (conveyance path RT2) to the color erasing section40.

The main CPU 61 instructs the conveyance control section 64 to carry outa control so that the rotation speed of the conveyance roller R based onthe driving of the motor M is faster than the general speed. Therotation speed of the conveyance roller R is controlled so that the heatcapacity per unit time applied to the sheet by the thermal head 41 ofthe color erasing section 40 is a value at which the fixation of therecording agent forming the image on the conveyed sheet does not occur.The conveyance control section 64 controls the driving of the motor M inresponse to the instruction of the main CPU 61 so that the conveyancespeed of the sheet becomes faster. In this case, the offset due to therecording agent which forms the image on the conveyed sheet is notcaused.

Then, the second conveyance path (conveyance path RT3) guides the sheetpassing through the color erasing section 40 to the first conveyancepath (conveyance path RT2). The first conveyance path (conveyance pathRT2) conveys the sheet conveyed by the second conveyance path(conveyance path RT3) to the reading section 30 (ACT 202). The readingsection 30 reads the images on the front side and the back side of theconveyed sheet to acquire image data (ACT 109). The following processingis the same as that in the first specific example.

In the color erasing apparatus 1 with such a constitution, it isdetermined whether or not the image formed on the sheet to be subjectedto color erasing processing is an image formed with color erasablerecording agent. In a case where the image is not an image formed withcolor erasable recording agent, the color erasing apparatus 1 carriesout a control so as not to carry out color erasing processing on thesheet. Then the color erasing apparatus 1 discharges the sheet to thereject tray 52. Thus, it is possible to reduce the occurrence of offsetcaused by the sheet on which an image is formed with recording agentcontaining color inerasable coloring agent.

Further, in the color erasing apparatus 1, the determination on whetheror not the image is formed with color erasable recording agent iscarried out based on a determination on whether or not there is a givenimage in the pre-determined detection target area. The detection targetarea is arranged at the front end part in the conveyance direction ofthe sheet. Thus, it is possible to determine whether or not to carry outcolor erasing processing at timing earlier than the conveyance. Further,the detection target area is also arranged at the rear end part in theconveyance direction of the sheet. Thus, it is possible to determinewhether or not to carry out color erasing processing at timing earlierthan the conveyance even if the front end part and the rear end part ofthe sheet are set incorrectly in the conveyance direction.

In the color erasing apparatus 1, the threshold value of the colordifference for each color of sheet is used when the given image 74 isdetected in the detection target area. Thus, it is possible to preventthat the given image 74 in the detection target area is not detected bymistake no matter whether or not the image is formed with color erasablerecording agent. For example, in a case where the color of the sheet isdark color, compared with the case where the color of the sheet iswhite, the color difference between the color of the given image 74 andthe color of the sheet is small. Therefore, if the threshold value ofthe color difference used in the case where the color of the sheet iswhite is applied to this case, there exists a possibility that the givenimage 74 cannot be detected. However, in the color erasing apparatus 1,such a problem is solved because the threshold value of the colordifference for each color of sheet is set as stated above.

Next, the color erasable recording agent mentioned above is described.In a case where the color erasable recording agent is toner, forexample, the toner is manufactured in the following way.

The preparation of atomized solution containing binder resin: Pes(Polyester) resin with a glass transition temperature Tg of 50 degreescentigrade and a softening point of 100 degrees centigrade is used asthe binder resin. The particle dispersion (atomized solution) containingbinder resin is manufactured with a high pressure homogenize using 30pts. mass of Pes resin, 3 pts. mass of anionic emulsifier (NEOPELEX G15,manufactured by Kao Corp.), 0.6 pts. mass of neutralizing agent(dimethylaminoethanol).

The preparation of release agent atomized solution: atomized solution ismanufactured using 30 pts. mass of rice WAX using the same manufacturingmethod of the binder resin.

The preparation of coloring agent: heating and dissolving the componentincluding 1 pts. mass of3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalideas the leuko dye; 5 pts. mass of 2,2-Bis (4-hydroxyphenyl)hexafluoropropane as color developing agent; and 50 pts. mass of diestercompound of pimelic acid and 2-(4-benzyloxy-phenyl) ethanol as colorerasing agent (temperature control agent); adding the mixture solutionof 20 pts. mass of aromatic polyvalent Isocyanate prepolymer asencapsulating agent and 40 pts. mass of ethyl acetate to 250 pts. massof 8% polyvinyl alcohol solution; and then emulsifying and dispersingthe mixture solution. Next, after stirring for an hour at a temperatureof 70 degrees centigrade, adding 2 pts. mass of water-soluble aliphaticmodified amine as reactant, and then keeping the solution at 90 degreescentigrade and meanwhile stirring the solution for about three hours toobtain leuco capsule particle. Then, putting the capsule particledispersion in a freezer (−30 degrees centigrade) to generate color,thereby obtaining blue coloring agent. The volume average particlediameter of the color generation particle C1 is 2 μm when measured bySALD7000 manufactured by Shimadzu Corporation.

The process of aggregation and fusion: aggregating 10 pts. mass ofencapsulated coloring agent, 283 pts. mass of atomized solutioncontaining binder resin, 17 pts. mass of release agent atomized solutionusing 100 pts. mass of aluminum sulfate [A12(SO4)3] 5% solution at 45degrees centigrade. Then, raising the temperature up to 65 degreescentigrade (temperature rising speed: 1 degree centigrade/min) andfusing, then rinsing and drying to obtain capsule color erasable toner.The amount of the coloring agent in the capsule color erasable toner is10 mass %.

The complete color erasing temperature of the toner is 95 degreescentigrade, and the color erasing starting temperature is 85 degreescentigrade, and further, the complete color generating temperature is −5degrees centigrade.

Next, the image forming apparatus which carries out image format ionwith the color erasable recording agent described above is described.FIG. 9 is an external view illustrating one example of an image formingapparatus 100 according to the embodiment. The image forming apparatus100 is, for example, a multi-function peripheral (MFP: MultifunctionPrinter). The image forming apparatus 100 reads the sheet to generatedigital data (image file).

The image forming apparatus 100 comprises a display section 40, ascanner section 50, a print section 60 and a tray 120. The image formingapparatus 100, which is not limited to an image forming apparatus forfixing a toner image, may be an inkjet type image forming apparatus.

FIG. 10 is a block diagram illustrating an example of the functionalconstitution of the image forming apparatus 100 according to theembodiment. The image forming apparatus 100 comprises a CPU (CentralProcessing Unit) 310, a network interface 320, a storage device 330, adisplay section 340, a scanner section 350, a print section 360, animage processing section 370, a system processing section 380, a pagememory 390 and a temporary storage section 410. Each section of theimage forming apparatus 100 is connected with each other through aninternal bus line 420, and is capable of carrying out data input/outputprocessing.

The CPU 310 operates, for example, as a control section, and controlsthe operation of each section of the image forming apparatus 100.

The network interface 320 carries out data transmission/reception withother apparatuses.

The storage device 330, which is, for example, a hard disk or a SSD(solid state drive), stores the data used by each section of the imageforming apparatus 100.

The display section 340 is, for example, a liquid crystal displayprovided with a touch panel. The display section 340 operates as anoutput interface to display characters and images. The display section340 may also operate as an input interface to receive an instructioninput from a user.

The scanner section 350 is, for example, a color scanner provided with aContact Image Sensor (CIS) and a Charge Coupled Devices (CCD) and thelike. The scanner section 350 reads, with a sensor, an image formed on asheet to generate digital data.

The print section 360 forms an image on the sheet with the colorerasable recording agent.

The image processing section 370 carries out image processing on thedigital data generated by the scanner section 350.

The system processing section 380 carries out DMA (Direct Memory Access)on the page memory 390.

The page memory 390 temporarily stores the digital data to be processed.

The temporary storage section 410 is, for example, a RAM (Random AccessMemory), and temporarily stores the data used by each section of theimage forming apparatus 100.

When carrying out image formation with color erasable recording agent,the image forming apparatus 100 with such a constitution forms the givenimage 74 in the detection target area 73, as shown in FIG. 3˜FIG. 5.

Next, a modification of the color erasing apparatus is described. Themain CPU 61 instructs the conveyance control section 64 not to conveythe sheet further than the conveyance path RT2 until the determinationin ACT 104 is completed. In this case, the conveyance control section 64controls the rotation of the conveyance roller R so that the sheet isnot conveyed further than the gate GT1 until the conveyance of the sheetis allowed. When the determination in ACT 104 is completed, the main CPU61 instruct s the conveyance control sect ion 64 to continue theconveyance of the sheet. At this time, the main CPU 61 controls theconveyance path serving as a conveyance destination of the sheet inresponse to the determination result.

In accordance with at least one embodiment described above, the main CPU61 is arranged to determine whether or not to carry out color erasingprocessing, thus, it is possible to reduce the occurrence of offsetcaused by the sheet on which an image is formed with recording agentcontaining color inerasable coloring agent.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the invention. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinvention. The accompanying claims and their equivalents are intended tocover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A color erasing apparatus, comprising: a firstconveyance roller to convey a sheet along a first conveyance path; asecond conveyance roller to convey the sheet having passed through thefirst conveyance path along a second conveyance path; a scannerconfigured to capture an image formed on the sheet passing the firstconveyance path; a color erasing section configured to erase the colorof the image formed with a color erasable recording agent on the sheetpassing the second conveyance path; and a control section configured todetermine whether the image on the sheet is formed with the colorerasable recording agent or the color inerasable recording agent basedon data of the image captured by the scanner, and configured to controlthe second conveyance roller, in a case where the image on the sheet wasformed with the color erasable recording agent, to convey the sheetalong the second conveyance path at a first speed, and in a case wherethe image formed on the sheet was formed with the color inerasablerecording agent, to convey the sheet along the second conveyance path ata second speed greater than the first speed.
 2. The color erasingapparatus according to claim 1, wherein the control section determinesthat the image on the sheet was formed with the color inerasablerecording agent, if a given image is not formed in a given area of thesheet, and wherein the color inerasable recording agent contains acoloring agent, color of which cannot be erased by heating.
 3. The colorerasing apparatus according to claim 1, wherein the control sectiondetermines that the image on the sheet was formed with the colorinerasable recording agent, if the given image is not formed in thegiven area located at a front end part of the sheet in a conveyancedirection in which the sheet is conveyed, and wherein the colorinerasable recording agent contains a coloring agent, color of whichcannot be erased by heating.
 4. The color erasing apparatus according toclaim 1, wherein the control section controls the first conveyanceroller not to convey the sheet to the second conveyance path so that thesheet is not subjected to color erasing processing by the color erasingsection.
 5. The color erasing apparatus according to claim 1, whereinthe control section controls a temperature of the color erasing sectionwhen the sheet passes through the color erasing section to prevent thetemperature from exceeding a fixing temperature of the recording agentcontaining coloring agent, color of which cannot be erased, so thatwhereas the sheet is subjected to color erasing processing by the colorerasing section, color of the image on the sheet is not erased.
 6. Thecolor erasing apparatus according to claim 1, wherein the controlsection controls the conveyance speed of the sheet when the sheet passesthrough the color erasing section to be so fast a speed that a heatcapacity required to fix the recording agent containing coloring agent,color of which cannot be erased, is not applied to the sheet, so thatwhereas the sheet is subjected to color erasing processing by the colorerasing section, color of the image on the sheet is not erased.
 7. Thecolor erasing apparatus according to claim 1, wherein the controlsection controls the first conveyance roller to stop conveying the sheetuntil how to control the sheet is determined.
 8. The color erasingapparatus according to claim 1, wherein the control section determines asheet color of the sheet and the color of the given image based on athreshold value of a color difference which differs according to thesheet color of the sheet.
 9. A color erasing system, comprising: animage forming apparatus configured to form a pre-determined image at apre-determined position when forming an image on a sheet with colorerasable recording agent serving as recording agent containing coloringagent the color of which can be erased by heating; and a color erasingapparatus comprising: a first conveyance roller for conveying a sheetalong a first conveyance path; a second conveyance roller for conveyingthe sheet having passed through the first conveyance path along a secondconveyance path; a scanner for capturing an image formed on the sheetpassing the first conveyance path; a color erasing section for erasingthe color of the image formed with the color erasable recording agent onthe sheet passing the second conveyance path; and a control section fordetermining whether the image on the sheet is formed with the colorerasable recording agent or the color inerasable recording agent basedon data of the image captured by the scanner, and controlling the secondconveyance roller, in a case where the image on the sheet was formedwith the color erasable recording agent, to convey the sheet along thesecond conveyance path at a first speed, and in a case where the imageon the sheet was formed with the color inerasable recording agent, toconvey the sheet along the second conveyance path at a second speedgreater than the first speed.
 10. A color erasing control method,comprising: conveying, by a first conveyance roller, a sheet along afirst conveyance path; conveying, by a second conveyance roller, thesheet having passed through the first conveyance path along a secondconveyance path; capturing, by a scanner, an image formed on the sheetpassing the first conveyance path; erasing, by a color erasing section,the color of the image formed with a color erasable recording agent onthe sheet passing the second conveyance path; determining, by a controlsection, whether the image on the sheet is formed with the colorerasable recording agent or the color inerasable recording agent basedon data of the image captured by the scanner; and controlling, by thecontrol section, the second conveyance roller, in a case where the imageon the sheet was formed with the color erasable recording agent, toconvey the sheet along the second conveyance path at a first speed, andin a case where the image on the sheet was formed with the colorinerasable recording agent, to convey the sheet along the secondconveyance path at a second speed greater than the first speed.